Currently, the liquid crystal display is widely used in various electronic products. With the continuous development of society, users have higher and higher requirement of the display screen color vividness of the liquid crystal display, which requires the color gamut of the liquid crystal display to be increasingly higher.
Usually, the liquid crystal display includes a liquid crystal panel and a backlight module that provides display backlight to the liquid crystal panel. The backlight module is one of the most important components of the liquid crystal display, and the color gamut of the display backlight provided by it directly determines the color gamut of the liquid crystal display. Generally, the color gamut of the display backlight is improved by applying quantum dots in the backlight module. For example, a quantum tube is formed by encapsulating quantum dots into a glass tube, and light emitted from a light source in the backlight module passes through the glass tube to excite quantum dots in the glass tube, so as to produce display backlight of a high color gamut.
In the prior art, the quantum tube is usually mounted and fixed with a plastic bracket to achieve a safe fixation of the quantum tube. As shown in FIG. 1, a quantum tube 40a is mounted in the quantum tube receiving cavity of a plastic bracket 20a that is completely fixed on an aluminum profile 10a through several screws 60a. 
During the researches, the inventor finds that after the plastic bracket 20a and the aluminum profile 10a are heated, the elongation amount of the plastic bracket between two fixing screws 60a is larger than the elongation amount of the aluminum profile 10a between the two fixing screws 60a since the thermal expansion coefficient of the plastic bracket 20a is larger than that of the aluminum profile 10a. As a result, the plastic bracket 20a is bent and deformed, and the glass tube of the quantum tube 40a has a poor plasticity, thus the quantum tube 40a finally will be bent and broken.